The government has gagged its own pesticide advisers, after they refused to back an application by the National Farmers Union to lift a ban on bee-harming chemicals. The gag is intended to prevent campaigners lobbying ministers on the issue, according to documents seen by the Guardian.

Neonicotinoids, the world’s most widely used insecticide, were banned in the European Union in 2013. Substantial scientific evidence indicates that the nerve agents cause serious harm to bees, whose #pollination is vital for many crops.

The National Farmers Union says oil seed rape is becoming impossible to grow without the pesticides and applied for an emergency lifting of the ban on two neonicotinoids.

The NFU told the Guardian the Expert Committee on Pesticides (ECP), part of the Health and Safety Executive, refused to back its request. Ministers said the final decision had yet to be made, but on Thursday the NFU submitted new applications targeting smaller areas of the country. Nearly one in 10 of Europe’s wild bee species face extinction, says study Read more The ECP website says that for openness and transparency, minutes of meetings are routinely published after three weeks. But the notes of a crucial 20 May meeting have yet to appear, as has the agenda of another meeting on 7 July.

An ECP official told campaigners from the Bee Coalition by email that: “We have been approached by the Department for Environment and Rural Affairs (Defra) who have requested that we postpone publication of the minutes [and July agenda].

“This is to enable government to have the time and space to consider applications for emergency authorisations without having to provide interim comment or provoking representations from different interest groups whose views on the issue are well known.”

The gagging by Defra appears to contravene the ECP’s terms of reference, which state that “the committee will make its scientific conclusions and recommendations available to the public and other interested parties in a way which aims to be comprehensive, clear and timely. The committee will decide its own publication schedule.” Bees are worth billions to farmers across the globe, study suggests Read more Furthermore, the government’s code of practice for science advisory committees states that they “should expect to operate free of influence from the sponsor department officials or ministers”.

Paul de Zylva, from Friends of the Earth and chair of the Bee Coalition of 10 NGOs, said: “The threat to Britain’s bees from rising pesticide use is of huge public interest. But the secrecy and lack of information surrounding this crucial issue is astonishing. If the government and farmers put as much effort into reversing bee decline as they do playing politics over pesticides and bee health we might have less of a bee problem.”

As well as the ECP’s meeting minutes, the NFU’s application forms have also been kept secret, despite requests from MPs for their publication. The farming minister, George Eustice said the information in the applications was commercially sensitive.

Zylva disputed the NFU’s suggestion that the pesticide ban had had a serious effect on crops. He pointed out that official statistics released earlier in July showed that, thanks to good weather, yields of oil seed rape actually rose by 23% in 2014, the year after the introduction of the neonicotinoid ban.

A spokeswoman for the NFU said: “Oil seed rape crops have been devastated and are impossible to grow in some areas of the country.”

She said crops harvested early in 2014 had been planted before the ban entered force on December 2013, and therefore had been treated with neonicotinoids. A survey by the #Agriculture and Horticulture Development Board of oil seed rape sown in winter 2014, after the ban, indicated that 3.5% of the crop had been lost to the flea beetle pest.

A Defra spokesman said: “The government is committed to ensuring pesticides are available when the regulators are satisfied and the scientific evidence shows they are safe to people and the environment.”

In July 2014, chemical company Syngenta made a similar emergency application to lift the ban on the neonicotinoid it manufactures. The bid failed after Syngenta withdrew the application, blaming the government for failing to make a decision in time for crop sowing.